1. Field of the Invention
The present invention relates to a liquid crystal display device that can prevent a cell guide for retaining a liquid crystal cell from falling away in assembling.
2. Description of Related Art
Liquid crystal display devices are slim in body, light in weight and low in power consumption, and have been widely used for notebook-size personal computers, monitors of personal computers, television sets for household use, etc. Such liquid crystal display devices each have a liquid crystal panel for displaying an image, and a backlight for radiating light from the rear face side of the panel. The light emitted by the backlight is made to pass through the liquid crystal panel or blocked by the liquid crystal panel, whereby an image is formed on the front side of the liquid crystal panel.
To achieve an image with a higher luminance and a less luminance non-uniformity in a liquid crystal display device, it is necessary that the backlight and liquid crystal panel be supported and fixed close to each other. The backlight is attached to a rear frame made of a metal, and retained by a light frame made of a resin from its upper face side. The light frame is fixed to the rear frame.
The liquid crystal panel has a cell guide which is a frame of a rectangular form, a diffusion plate and a diffusion sheet, both for diffusing light from the backlight, and a liquid crystal cell having a pair of rectangular glass substrates with liquid crystal filled in the space therebetween. In the liquid crystal panel, the diffusion plate and the diffusion sheet are pressed by the cell guide against the upper face of the rear frame and the light frames and fixed. The liquid crystal cell is retained on the upper face side of the cell guide. In the condition where the cell guide holds down the diffusion plate and the diffusion sheet toward the upper face of the rear frame and the light frames and retains the liquid crystal cell on its upper face, a bezel, which is a frame having a rectangular form, is put on the cell guide from the upper face side of the cell guide, followed by bolting together the bezel, the cell guide and the rear frame or the light frames. Thus, a liquid crystal display device that can offer an image with a higher luminance and a less luminance non-uniformity is fabricated.
In assembling the liquid crystal panel as described above, the diffusion plate and the diffusion sheet are placed on the upper face of the rear frame and the light frames, and then the cell guide is placed thereon from the upper face side. Further, the cell guide is secured by bolts together with the bezel and the rear frame or the light frame. As a result, if the cell guide, and the rear frame and the light frames are out of their right positions even slightly, the work to adjust their relative positions becomes necessary, which lowers the working efficiency. In addition, when the work to adjust their relative positions is carried out, the diffusion plate and the diffusion sheet held down by the cell guide and the liquid crystal cell retained on the upper face side of the cell guide can be out of position, which can pose an additional troublesome work.
To solve such problems, a conventional liquid crystal display device has bosses formed on the light frame and protruding from the upper face thereof, in which positioning of the cell guide with respect to the rear frame and the light frames is performed by fitting the bosses in corresponding boss holes formed in the cell guide.
In recent years, liquid crystal display devices have tended to be upsized. A member composed of four cell guide pieces each including a corner portion has been used as the cell guide with the upsizing of liquid crystal display devices. Also, for the bezel, a member composed of four bezel pieces each making one side of a rectangle has been used. As the cell guide can be divided, just engaging the boss holes of the cell guide with the bosses formed on the upper face of the light frame as conventionally performed can bring the diffusion plate, the diffusion sheet and the cell guide out of position, making the work difficult.
Hence, adopted is a method which includes: placing the cell guide on the rear frame and the light frames from the upper face; in this condition, temporarily fixing the cell guide to the rear frame and the light frames by bolts; and placing the bezel thereon and securing them together by bolts.
Also, there has been known a liquid crystal display device as disclosed by JP-A-5-66390, in which electrically-insulative retaining members for retaining a support frame, a liquid crystal display panel, a light-guide plate, a light source and an input-output lead wire are used to perform positioning of the respective members.
Further, according to the invention disclosed by JP-A-2000-258756, a liquid crystal module is presented, in which when an outer frame is attached, an engagement nail formed on a resin frame to be placed inside the module is engaged with a hole formed in the outer frame, whereby the outer frame is attached.
Further, according to the invention disclosed by JP-A-2003-195263, a liquid crystal display device is presented, in which hooks are formed on a frame for covering a peripheral portion of a liquid crystal element, the hooks are used to fasten the liquid crystal element between the frame and a metal housing, and therefore the liquid crystal element is fixed by engaging the hooks with the metal housing.
However, the cell guide will end up as being bolted together with the bezel and the rear frame or the light frames. Therefore, two types of bolts, namely ones for temporarily retaining the cell guide and ones for fastening the bezel and cell guide together, are required, which increases the number of constituent members and the number of steps for the attachment, and thus raises the manufacturing cost.
In addition, the bezel needs through-holes for temporary retaining thereof and through-holes for securing it together with the other member. Hence, the strength of the bezel is deteriorated correspondingly to the through-holes thus formed, and large amounts of human efforts and time are required to manufacture the bezel.
Further, according to the invention disclosed by JP-A-5-66390, the retaining members for positioning constituent members are provided, and correspondingly the number of constituent members is increased and thus the manufacturing cost is raised.
Moreover, as to a large-size liquid crystal display device, it is difficult to use an outer frame as the bezel to firmly hold down the liquid crystal cell including the cell guide as in the case of the invention disclosed by JP-A-2000-258756. In addition, with this structure, it is necessary to deform the outer frame, for which it is undesirable to be deformed, in order to engage the outer frame with engagement nails.